Blowing agent compositions for insulating foams

ABSTRACT

Disclosed is a blowing agent composition comprising a hydrofluoroolefins (HFO) and a branched hydrocarbon, and a foamable polymer composition comprising the blowing agent composition. Also disclosed is a method of making a polymer foam utilizing a blowing agent composition comprising an HFO and a branched hydrocarbon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/425,359, filed on May 29, 2019, which claims priority to and anybenefit of U.S. Provisional Application No. 62/677,248, filed on May 29,2018, the entire contents of which are incorporated herein by reference.

FIELD OF DISCLOSURE

This invention relates to blowing agent compositions for insulatingfoams made from thermoplastic polymers. This invention further relatesto insulating foams made utilizing these blowing agent compositions.

BACKGROUND OF THE INVENTION

In the past, insulating foams have been made utilizing halogenatedblowing agents to create gas-filled cells within the insulating foams.Chlorofluorocarbons (CFCs) and chlorofluorohydrocarbons (HCFCs) wereamong the earliest blowing agents. However, suspected environmentalconcerns about chlorinated blowing agents, including possible ozonedepletion in the upper atmosphere, led to the development of blowingagents that were considered less damaging to the environment. Theselater blowing agents included fluorocarbons (FCs) and fluorohydrocarbons(HFCs).

Recently, newer hydrofluoroolefins (HFOs) have been developed. HFOblowing agents are believed to be more environmentally friendly thantraditional halogenated blowing agents. For example, HFOs ae believed tohave reduced Ozone Depletion Potential (ODP) and reduced Global WarmingPotential (GWP) compared to traditional FC and HFC halogenated blowingagents.

Other than halogenated blowing agents, other types of blowing agentshave been investigated. For example, hydrocarbons such as pentane,hexane, cyclopentane and similar compounds have also been considered asblowing agents. These hydrocarbons are highly flammable and volatile,thereby raising both safety concerns and concerns about the emission ofvolatile organic compounds (VOCs). Carbon dioxide (CO₂) is an attractivecandidate as a blowing agent, from both the environmental and economicstandpoints. Successfully using CO₂ as a blowing agent is challengingdue to the relatively low solubility, high diffusivity and poorprocessability of CO₂ in the polymers typically used as the matrixpolymers of insulating foams. CO₂ also has an increased thermalconductivity relative to that of HCFCs and HFCs, with CO₂-blown foamexhibiting about 10-20% lower insulation values than corresponding foamsproduced with HCFCs or HFCs.

To ensure that an insulating foam has the desired properties (e.g., lowdensity, good thermal resistance, etc.), it is important that theblowing agent be sufficiently soluble in the polymer matrix of theinsulating foam. It has been found that HFO blowing agents alone may notbe sufficiently soluble in the polymer matrix of the insulating foam,resulting in insulating foams that are too dense or which allowunacceptably high thermal conductivity. To improve the properties of theresulting insulating foam, blowing agent compositions containingcombinations of HFOs with HCFCs, HFCs, carbon dioxide, water, and othersuch mixtures have been attempted, with mixed results.

SUMMARY OF THE INVENTION

The objectives of the present invention include improved blowing agentcompositions comprising an HFO and a branched hydrocarbon. Theobjectives further include a foamable polymer composition incorporatingthe improved blowing agent, and an improved method of making polymerfoams using the improved blowing agent.

In an exemplary embodiment of the invention, a blowing agent compositionis provided comprising a hydrofluoroolefin (HFO) and a branchedhydrocarbon. In some exemplary embodiments, the blowing agent containsessentially no water.

In an exemplary embodiment of the invention, a foamable polymercomposition is provided comprising a matrix polymer and a blowing agentcomposition comprising an HFO and a branched hydrocarbon. In someexemplary embodiments, the foamable polymer composition containsessentially no water.

In an exemplary embodiment of the invention, a method of manufacturing apolymer foam is provided, comprising: melting a matrix polymer; mixing ablowing agent composition comprising an HFO and a branched hydrocarbonwith the matrix polymer melt to form a foamable polymer composition; andextruding the foamable polymer composition to form a polymer foam. Insome exemplary embodiments, the foamable polymer composition containsessentially no water.

DESCRIPTION OF THE DRAWINGS

Example embodiments of the invention will be apparent from the moreparticular description of certain example embodiments of the inventionprovided below and as illustrated in the accompanying drawings.

FIG. 1 is a graph of the thermal insulating properties for foamformulations comprising various blowing agent compositions after 7 daysaging.

FIG. 2 is a graph of thermal insulating properties for foam formulationscontaining various concentrations of HFO-1234ze and n-pentane as thefoams age.

FIG. 3 is a graph of thermal insulating properties for foam formulationscontaining HFO-1234ze and various co-blowing agents as the foams age.

FIG. 4 is a graph of the data in FIG. 3 normalized for the mole %concentration of each co-blowing agent.

FIG. 5 is a graph of thermal insulating properties for foam formulationscontaining HFO-1234ze and isobutane at various densities as the foamsage.

FIG. 6 is a graph of thermal insulating properties of foam formulationscontaining HFO-1234ze and various hydrocarbon co-blowing agents atvarious densities after 7 days aging.

FIG. 7 is a graph of thermal insulating properties for foam formulationscontaining HFO-1234ze, isobutane, and carbon dioxide.

These drawings have been provided to assist in the understanding of theexample embodiments of the invention as described in more detail belowand should not be construed as unduly limiting the invention.

DETAILED DESCRIPTION

A polymer foam composition, along with a method for making polymer foam,is described in detail herein. The composition and method for makingpolymer foam disclosed herein includes blowing agent compositioncomprising a hydrofluoroolefin (HFO) and a branched hydrocarbon. In someexemplary embodiments, the blowing agent contains essentially no wateror carbon dioxide. The resulting polymer foam has reduced thermalconductivity, and therefore improved insulation properties, whencompared to blowing agents comprising HFO and linear hydrocarbons. Theseand other features of the polymer foam, as well as some of the manyoptional variations and additions, are described in detail hereafter.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Any methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention. Any references citedherein, including published or corresponding U.S. or foreign patentapplications, issued U.S. or foreign patents, or any other references,are each incorporated by reference in their entireties, including alldata, tables, figures, and text presented in the cited references.

As used in the description of the invention and the appended claims, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. To theextent that the term “includes” or “including” is used in thespecification or the claims, it is intended to be inclusive in a mannersimilar to the term “comprising” as that term is interpreted whenemployed as a transitional word in a claim. Furthermore, to the extentthat the term “or” is employed (e.g., A or B) it is intended to mean “Aor B or both.” When the applicants intend to indicate “only A or B butnot both” then the term “only A or B but not both” will be employed.Thus, use of the term “or” herein is the inclusive, and not theexclusive use.

Numerical ranges as used herein are intended to include every number andsubset of numbers within that range, whether specifically disclosed ornot. Further, these numerical ranges should be construed as providingsupport for a claim directed to any number or subset of numbers in thatrange. For example, a disclosure of from 1 to 10 should be construed assupporting a range of from 2 to 8, from 3 to 7, from 5 to 6, from 1 to9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

All references to singular characteristics or limitations of the presentdisclosure shall include the corresponding plural characteristic orlimitation, and vice versa, unless otherwise specified or clearlyimplied to the contrary by the context in which the reference is made.

As used herein, unless specified otherwise, the values of theconstituents or components of the polymer foam, the flame retardantcomposition, or other compositions are expressed in weight percent or %by weight of each ingredient in the composition. The values providedinclude up to and including the endpoints given. Unless otherwisespecified, the terms “% by weight” and “wt. %” are used interchangeablyand are meant to indicate a percentage based on 100% of a total weight.In some embodiments, the amount of blowing agent(s) is given in terms ofmoles/100 g, which is meant to indicate the number of moles of thespecified blowing agent per 100 grams of matrix polymer.

As used herein, the term “polymer” is generic to the terms“homopolymer,” “copolymer,” “terpolymer,” and combinations ofhomopolymers, copolymers, and/or terpolymers.

As used herein, the term “matrix polymer” refers to the polymer orpolymer mixture forming the bulk of the foamable polymer composition andthe polymer foam product. The matrix polymer provides strength,flexibility, toughness, and durability to the final product.

As used herein, the term “matrix polymer composition” refers to acomposition comprising the matrix polymer(s) with other optionaladditives, such as stabilizers, processing aids, colorants, fireretardants, etc.

As used herein, the term “blowing agent” refers to a liquid or gaseouscompound or mixture which, when mixed with a molten matrix polymercomposition under pressure (such as the pressure within an extruder),forms a foamable polymer composition, and which converts to tiny pocketsof gas when the composition is released from pressure, thereby causingthe foamable polymer composition to foam. As used herein, the term“co-blowing agent” refers to a second (third, fourth, etc.) blowingagent in a blowing agent composition.

As used herein, the term “branched hydrocarbon” refers to a compoundconsisting of carbon and hydrogen atoms, where the carbon atoms arearranged in a branched rather than a linear or cyclic conformation.Exemplary branched hydrocarbons include isobutane, isopentane,neopentane, isohexane, 3-methylpentane, 2,3-dimethylbutane, neohexane,isoheptane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane,2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, and2,2,3-trimethylbutane.

The general procedure utilized in the preparation of extruded syntheticfoam bodies generally includes the steps of melting a matrix polymercomposition, then incorporating a blowing agent composition into thepolymer melt to form a foamable polymer composition, under conditionsthat provide for the thorough mixing of the blowing agent compositionand the matrix polymer while preventing the foamable polymer compositionfrom foaming prematurely, e.g., under pressure. Other additives (e.g.,stabilizers, processing aids, colorants, fire retardants, etc.) may alsobe added into the foamable polymer composition. This foamable polymercomposition is then typically extruded through a single or multi-stageextrusion die to cool and reduce the pressure on the foamable polymercomposition, allowing the foamable polymer composition to foam andproduce a foamed product. As will be appreciated, the relativequantities of the polymer(s), blowing agent(s) and additives in thefoamable polymer composition, as well as the temperature and the mannerin which the pressure is reduced, may affect the qualities andproperties of the resulting foam product.

Blowing Agent Composition

In selecting a blowing agent composition, the solubility of the blowingagent composition in the matrix polymer is an important consideration.For example, the combination of pentane and a CFC such as Freon 11 and12 is partially soluble in PS and has been used for generating PS foamsthat exhibited a generally acceptable appearance and physical propertiessuch as surface finish, cell size and distribution, orientation,shrinkage and stiffness. Fluorocarbons (FCs) and hydrofluorocarbons(HFCs), such as 1,1,1,2-tetrafluoroethane (HFC-134a) and1,1-difluoroethane (HFC-152a), are thought to be much more ozonefriendly than CFCs, but they tend to be less soluble in PS. Newerhydrofluoroolefin (HFO) blowing agents are believed to be moreenvironmentally friendly than traditional halogenated blowing agents.However, many HFOs, such as tetrafluoropropenes, have poor solubility inPS. When these HFOs are used as blowing agents without a co-blowingagent to make PS foam, the HFO tends to remain undissolved in the PSmatrix, which creates large blow-holes and other defects in the foamproduct during the extrusion of the foamable polymer composition. Thepoor solubility of HFO blowing agents in PS may also detrimentallyimpact the long-term insulating properties of the foam.

HFO blowing agents with co-blowing agents, such as hydrocarbons,hydrofluorocarbons, carbon dioxide, and water, have been studied todetermine if the co-blowing agents improve the solubility of HFO in thematrix polymer. Hydrocarbons are soluble in PS, and are thought toimprove the solubility of HFO in PS as well.

The inventors have discovered that HFO blowing agent compositions withbranched hydrocarbon co-blowing agents unexpectedly form foams withimproved insulating properties, when compared to foams made with blowingagent compositions comprising HFO with linear hydrocarbons, cyclichydrocarbons, or HFC co-blowing agents, excluding branched hydrocarbons.Without wishing to be bound by theory, the inventors believe thatbranched hydrocarbons are superior co-blowing agents because of thecompactness of the branched hydrocarbon molecule. The pendant branchedgroups (e.g., methyl groups) on branched hydrocarbons means that thesemolecules are more compact and have a smaller surface area than do themolecules of linear or cyclic hydrocarbons with the same number ofcarbon atoms. The intermolecular attractive forces, which depend on thesurface area of a molecule, are also smaller between branchedhydrocarbons than between linear or cyclic hydrocarbons with the samenumber of carbon atoms. Consequently, the boiling points of branchedhydrocarbons are less than the corresponding linear or cyclichydrocarbons, and the lower boiling points result in higher vaporpressure for the branched hydrocarbons. The higher vapor pressure of thebranched hydrocarbons leads to more branched hydrocarbon gas in eachcell of the insulating foam. Because a blowing agent must be in gaseousform to be an effective insulating gas, blowing agents with higher vaporpressures, and therefore more gas in the foam cells, tend to haveimproved insulating properties.

The hydrofluoroolefin blowing agent in the blowing agent composition ofthe present invention may include, for example, 3,3,3-trifluoropropene(HFO-1243zf); 2,3,3-trifluoropropene; (cis and/ortrans)-1,3,3,3-tetrafluoropropene (HFO-1234ze), particularly the transisomer; 1,1,3,3-tetrafluoropropene; 2,3,3,3-tetrafluoropropene(HFO-1234yf); (cis and/or trans)-1,2,3,3,3-pentafluoropropene(HFO-1225ye); 1,1,3,3,3-pentafluoropropene (HFO-1225zc);1,1,2,3,3-pentafluoropropene (HFO-1225yc); hexafluoropropene (HFO-1216);2-fluoropropene, 1-fluoropropene; 1,1-difluoropropene;3,3-difluoropropene; 4,4,4-trifluoro-1-butene;2,4,4,4-tetrafluoro-1-butene; 3,4,4,4-tetrafluoro-1-butene;octafluoro-2-pentene (HFO-1438);1,1,3,3,3-pentafluoro-2-methyl-1-propene; octafluoro-1-butene;2,3,3,4,4,4-hexafluoro-1-butene; 1,1,1,4,4,4-hexafluoro-2-butene(HFO-1336m/z); 1,2-difluoroethene (HFO-1132);1,1,1,2,4,4,4-heptafluoro-2-butene; 3-fluoropropene,2,3-difluoropropene; 1,1,3-trifluoropropene; 1,3,3-trifluoropropene;1,1,2-trifluoropropene; 1-fluorobutene; 2-fluorobutene;2-fluoro-2-butene; 1,1-difluoro-1-butene; 3,3-difluoro-1-butene;3,4,4-trifluoro-1-butene; 2,3,3-trifluoro-1-butene; 1,1,3,3-tetrafluoro-1-butene; 1,4,4,4-tetrafluoro-1-butene;3,3,4,4-tetrafluoro-1-butene; 4,4-difluoro-1-butene;1,1,1-trifluoro-2-butene; 2,4,4,4-tetrafluoro-1-butene;1,1,1,2-tetrafluoro-2 butene; 1,1,4,4,4-pentafluoro-1-butene;2,3,3,4,4-pentafluoro-1-butene; 1,2,3,3,4,4,4-heptafluoro-1-butene;1,1,2,3,4,4,4-heptafluoro-1-butene; and1,3,3,3-tetrafluoro-2-(trifluoromethyl)-propene. In some exemplaryembodiments, the blowing agent or co-blowing agents include HFO-1234ze.

The branched hydrocarbon co-blowing agent in the blowing agentcomposition of the present invention may include, for example, branchedbutanes, pentanes, hexanes, and heptanes. Preferred branched hydrocarbonco-blowing agents include, but are not limited to, isobutane,isopentane, neopentane, isohexane, 3-methylpentane, 2,3-dimethylbutane,neohexane, isoheptane, 3-methylhexane, 2,2-dimethylpentane,2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane,3-ethylpentane, and 2,2,3-trimethylbutane. In some exemplaryembodiments, the blowing agent or co-blowing agents include isobutane,isopentane, or combinations thereof.

In certain exemplary embodiments, the HFO blowing agent comprises fromabout 14% to about 89% by weight of the total weight of the blowingagent composition, including from about 15% to about 80%, including fromabout 20% to about 75%, including from about 25% to about 70%, includingfrom about 30% to about 65%, including from about 35% to about 60%, andincluding from about 38% to about 55% by weight of the total weight ofthe blowing agent composition. In some exemplary embodiments, the HFOblowing agent comprises less than 50% by weight of the total blowingagent composition.

In certain exemplary embodiments, the branched hydrocarbon co-blowingagent comprises from about 5.0% to about 85% by weight of the totalweight of the blowing agent composition, including from about 7.0% toabout 50%, including from about 9.0% to about 45%, including from about10% to about 40%, including from about 12% to about 35%, including fromabout 12.3% to about 32%, including about 12.5% to about 30%.

In certain exemplary embodiments, the blowing agent composition furtherincludes at least one secondary co-blowing agent, such as one or morehydrofluorocarbons (“HFC”), hydrochlorofluorocarbons (“HCFO”), carbondioxide, and water. In some exemplary embodiments, the blowing agentcomposition includes two or more secondary co-blowing agents, such as ahydrofluorocarbon and carbon dioxide. In some exemplary embodiments, theblowing agent composition is free of a secondary co-blowing agent. Insome exemplary embodiments, the blowing agent formulation is free ofcarbon dioxide and/or water. In various exemplary embodiments, theblowing agent composition is free of a hydrofluorocarbon.

In some exemplary embodiments, the secondary co-blowing agent maycomprise one or more hydrofluorocarbons. The specific hydrofluorocarbonutilized is not particularly limited. A non-exhaustive list of examplesof suitable blowing HFC blowing agents include 1,1-difluoroethane(HFC-152a), 1,1,1,2-tetrafluoroethane (HFC-134a),1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1-trifluoroethane (HFC-143a),difluoromethane (HFC-32), 1,3,3,3-pentafluoropropane (HFO-1234ze),pentafluoro-ethane (HFC-125), fluoroethane (HFC-161),1,1,2,2,3,3-hexafluoropropane (HFC-236ca), 1,1,1,2,3,3-hexafluoropropane(HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa),1,1,1,2,2,3-hexafluoropropane (HFC-245 ca), 1,1,2,3,3-pentafluoropropane(HFC-245 ea), 1,1,1,2,3 pentafluoropropane (HFC-245 eb),1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,4,4,4-hexafluorobutane(HFC-356mff), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), and combinationsthereof. In some exemplary embodiments, the secondary co-blowing agentcomprises HFC-152a.

The secondary co-blowing agent may also comprise one or morehydrochlorofluoroolefins (HCFO), such as HCFO-1233;1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124);1,1-dichloro-1-fluoroethane (HCFC-141b); 1, 1,1,2-tetrafluoroethane(HFC-134a); 1,1,2,2-tetrafluoroethane (HFC-134);1-chloro-1,1-difluoroethane (HCFC-142b); 1,1,1,3,3-pentafluorobutane(HFC-365mfc); 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea);tnchlorofluoromethane (CFC-11); dichlorodifluoromethane (CFC-12); anddichlorofluoromethane (HCFC-22).

The term “HCFO-1233” is used herein to refer to alltrifluoromonochloropropenes. Among the trifluoromonochloropropenes areincluded both cis- and trans-1,1,1-trifluo-3,chlororopropene(HCFO-1233zd or 1233zd). The term “HCFO-1233zd” or “1233zd” is usedherein generically to refer to 1,1,1-trifluo-3-chloro-propene,independent of whether it is the cis- or trans-form. The terms “cisHCFO-1233zd” and “trans HCFO-1233zd” are used herein to describe thecis- and trans-forms or trans-isomer of 1,1,1-trifluo,3-chlororopropene,respectively.

In certain exemplary embodiments, the secondary co-blowing agentcomprises from 0 to about 90% by weight off the blowing agentcomposition, including about 0.5% to about 89% by weight of the totalweight of the blowing agent composition, including from about 1% toabout 50%, including from about 3% to about 25%, including from about 5%to about 20%, including from about 7% to about 15%, and including fromabout 7.5% to about 13% by weight of the total weight of the blowingagent composition.

In certain exemplary embodiments, the total blowing agent composition ispresent in an amount from about 2% to about 15% by weight, and in someembodiments, from about 3% to about 10% by weight, or from about 4% toabout 9% by weight (based upon the total weight of the foamablecomposition, excluding the blowing agent composition). In some exemplaryembodiments, the total blowing agent composition is present in an amountfrom about 6.8 to about 8.0% by weight, including about 7.3 to about7.9% by weight, based on the total weight of the foamable composition,excluding the blowing agent composition.

In certain exemplary embodiments, the HFO blowing agent comprises fromabout 1% to about 8% by weight of the total weight of all ingredients inthe foamable composition, including from about 1.5% to about 7.5%,including from about 2% to about 7%, including from about 2.5% to about6.5%, including from about 3% to about 6%, including from about 3.5% toabout 5.5%, including from about 4% to about 5%, and including about4.5% by weight of the total weight of all ingredients in the foamablecomposition.

In certain exemplary embodiments, the HFO comprises from about 0.004moles/100 g to about 0.140 moles/100 g of the matrix polymer, includingfrom about 0.007 moles/100 g to about 0.125 moles/100 g, including fromabout 0.009 moles/100 g to about 0.120 moles/100 g, including from about0.010 moles/100 g to about 0.108 moles/100 g, including from about 0.015moles/100 g to about 0.0999 moles/100 g, including from about 0.017moles/100 g to about 0.091 moles/100 g, including from about 0.019moles/100 g to about 0.085 moles/100 g, and including about 0.020 toabout 0.075 moles/100 g of the matrix polymer. In some exemplaryembodiments, the HFO blowing agent comprises less than 0.05 moles/100grams of matrix polymer, including less than 0.045 moles/100 g, lessthan about 0.03 moles/100 g, less than 0.025 moles/100 g, less than0.023 moles/100 grams, and 0.021 moles/100 grams matrix polymer.

In certain exemplary embodiments, the branched hydrocarbon co-blowingagent comprises from about 0.05% to about 6% by weight of the totalweight of all ingredients in the foamable composition, including fromabout 0.1% to about 5.5%, including from about 0.5% to about 5%,including from about 0.8% to about 4.5%, including from about 0.9% toabout 4%, and including about 1.0% by weight of the total weight of allingredients. In certain exemplary embodiments, the branched hydrocarbonco-blowing agent comprises from about 0.0005 moles/100 g to about 0.150moles/100 g of the matrix polymer, including from about 0.0010 mole/100g to about 0.10 moles/100 g, including from about 0.0050 moles/100 g toabout 0.085 moles/100 g, including from about 0.0080 moles/100 g toabout 0.078 moles/100 g, including from about 0.009 moles/100 g to about0.065 moles/100 g, and including about 0.0100 to about 0.020 moles/100 gof the matrix polymer.

In certain exemplary embodiments, the one or more secondary co-blowingagent comprises from about 0.05% to about 6% by weight of the totalweight of all ingredients, in the foamable composition, including fromabout 0.1% to about 5.5%, including from about 0.5% to about 5%,including from about 0.8% to about 4.5%, including from about 0.9% toabout 4%, and including about 1.0% by weight of the total weight of allingredients.

Matrix Polymer

The matrix polymer forms the bulk of the foamable polymer mixture andprovides strength, flexibility, toughness, and durability to the finalproduct. The matrix polymer is not particularly limited, and generally,any polymer capable of being foamed may be used as the matrix polymer inthe foamable polymer mixture. The matrix polymer may be a thermoplasticor thermoset polymer. In some embodiments, the matrix polymer maycomprise a single polymer. In some embodiments, the matrix polymer maycomprise a blend of two or more polymers. In some embodiments, thematrix polymer may be selected to provide sufficient mechanical strengthto the final polymer foamed product. In some embodiments, the matrixpolymer may be selected to be compatible with the process utilized toform final polymer foam product. In some embodiments, the matrix polymeris chemically stable, that is, generally non-reactive, within theexpected temperature range experienced by the matrix polymer duringformation and subsequent use in a polymer foam.

The matrix polymer may be present in the foamable polymer mixture in anamount from at least about 50 wt. % (based on the total weight of allingredients excluding the blowing agent composition), in an amount fromabout 60 wt. % to about 100 wt. %, in an amount from about 70 wt. % toabout 99 wt. %, in an amount from about 75 wt. % to about 98 wt. %, inan amount from about 80 wt. % to about 96 wt. %, or in an amount fromabout 85 wt. % to about 95 wt. %. In certain exemplary embodiments, thematrix polymer may be present in an amount from about 80 wt. % to about100 wt. %.

Non-limiting examples of suitable matrix polymers include alkenylaromatic polymers, styrenic polymers, polystyrene (PS), styreniccopolymers, styrenic block copolymers, copolymers of styrene andbutadiene, styrene acrylonitrile (SAN), acrylonitrile butadiene styrene,acrylic/styrene/acrylonitrile block terpolymer (ASA), styrene maleicanhydride copolymer (SMA), styrene methyl methacrylate copolymer (SMMA),polyolefins, polyethylene (PE), polypropylene (PP), copolymers ofethylene and propylene, copolymers of vinyl acetate and ethylene,polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC),polycarbonates, polyisocyanurates, polyesters, polyethyleneterephthalate (PET), polyacrylic acid esters, polymethylmethacrylate(PMMA), polyphenylene oxide, polyurethanes, phenolics, polysulfone,polyphenylene sulfide, acetal resins, polyamides, polyaramides,polyimides, polyetherimides, rubber modified polymers, thermoplasticpolymer blends, and combinations thereof.

In some exemplary embodiments, the matrix polymer is an alkenyl aromaticpolymer material. Suitable alkenyl aromatic polymer materials includealkenyl aromatic homopolymers and copolymers of alkenyl aromaticcompounds and copolymerizable ethylenically unsaturated co-monomers. Inaddition, the alkenyl aromatic polymer material may include minorproportions of non-alkenyl aromatic polymers. The alkenyl aromaticpolymer material may be formed of one or more alkenyl aromatichomopolymers, one or more alkenyl aromatic copolymers, a blend of one ormore of each of alkenyl aromatic homopolymers and copolymers, or blendsthereof with a non-alkenyl aromatic polymer.

Examples of alkenyl aromatic polymers include, but are not limited to,those alkenyl aromatic polymers derived from alkenyl aromatic compoundssuch as styrene, styrene acrylonitrile (SAN) copolymers, alpha-methylstyrene, ethylstyrene, vinyl benzene, vinyl toluene, chlorostyrene, andbromostyrene. In at least one embodiment, the alkenyl aromatic polymercomprises polystyrene (PS).

In certain exemplary embodiments, minor amounts of monoethylenicallyunsaturated monomers such as C2 to C6 alkyl acids and esters, ionomericderivatives, and C4 to C8 dienes may be copolymerized with alkenylaromatic monomers to form the alkenyl aromatic polymer. Non-limitingexamples of copolymerizable monomers include acrylic acid, methacrylicacid, ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleicanhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butylacrylate, methyl methacrylate, vinyl acetate, and butadiene.

In certain exemplary embodiments, the matrix polymer may be formedentirely of polystyrene. In certain exemplary embodiments, the matrixpolymer may be formed substantially of (e.g., greater than 95 wt. %) ofpolystyrene. In certain exemplary embodiments, the matrix polymer may beformed of from about 40-100 wt. % of polystyrene, including from about45-99 wt. %, including from about 50-98 wt. %, including from about55-97 wt. %, including from about 60-96 wt. %, including from about65-95 wt. %, including from about 70-94 wt. %, including from about75-93 wt. %, including from about 80-92 wt. %, including from about85-91 wt. %, including from about 80-90 wt. % of polystyrene.

In certain exemplary embodiments, the polymer foam may comprise at leastone optional additive including, but not limited to, antioxidants,thermal stabilizers, UV stabilizers, acid scavengers, flame retardantcompositions, synergists, nucleating agents, plasticizing agents,pigments, elastomers, processing agents, extrusion aids, fillers,antistatic agents, biocides, termite-ocides, colorants, oils, or waxes.In certain exemplary embodiments, the polymer foam may comprise amixture of additives. These optional additives may be included inamounts necessary to obtain desired characteristics of the foamablepolymer mixture or resultant polymer foam. The additives may be added tothe foamable polymer mixture, or they may be incorporated before,during, or after the polymerization process used to make the matrixpolymer.

In certain exemplary embodiments, the polymer foam includes one or moreprocessing aids, such as a carbonate composition. Exemplary carbonatecompositions include propylene carbonate, dimethyl carbonate, butylenecarbonate, ethylene carbonate, and the like. The one or more processingaids may be included in the polymer foam material in an amount from 0 to20% by weight, including about 0.05 to about 17% by weight, about 0.1 toabout 15% by weight, about 1.0 to about 10% by weight, about 1.5 toabout 8% by weight, and about 2 to about 5% by weight.

Methods of Manufacture

Polymer foams comprising the blowing agent composition may be extrudedfoams or expanded foams. These polymer foams may be made by modifyingknown manufacturing methods using typical manufacturing equipment.

In some embodiments, the polymer foams of the present disclosure areextruded polymer foams made by an extrusion method. The extrusionapparatus may comprise a single or twin screw extruder including abarrel surrounding a screw on which a spiral flight is provided,configured to compress, and thereby, heat and melt the materialintroduced into the screw extruder. The matrix polymer and optionaladditives form a matrix polymer mixture, which may be fed into the screwextruder as a flowable solid, such as beads, granules, or pellets, or asa liquid or semi-liquid melt, from one or more feed hoppers.

As the matrix polymer mixture advances through the screw extruder, thedecreasing spacing of the flight defines a successively smaller spacethrough which the matrix polymer mixture is forced by the rotation ofthe screw. This decreasing volume acts to increase the pressure of thematrix polymer mixture to obtain a polymer melt (if solid startingmaterial was used) and/or to increase the pressure of the polymer melt.

As the matrix polymer mixture advances through the screw extruder, aport configured for injecting one or more additives into the polymermixture may be provided through the barrel. In some embodiments,additives such as processing aids, nucleating agents, flame retardantagents, antioxidants, or stabilizers may also be introduced to thepolymer mixture through the port. Similarly, one or more additionalports may be provided through the barrel for injecting one or moreblowing agent compositions into the polymer mixture. In someembodiments, one or more optional additives and blowing agentcompositions are introduced through a single port. In some embodiments,optional additives and blowing agent compositions, are introducedthrough a plurality of ports. Once these additives and blowing agentcompositions have been introduced into the matrix polymer mixture, theresulting mixture is subjected to some additional blending sufficient todistribute each of the additives generally uniformly throughout thepolymer mixture to obtain an extrusion composition.

This extrusion composition is then forced through an extrusion die, andexits the die into a region of reduced pressure (which may be belowatmospheric pressure), thereby allowing the blowing agent composition toexpand and produce a polymer foam material. This pressure reduction maybe obtained gradually as the extrusion composition advances throughsuccessively larger openings provided in the die or through somesuitable apparatus provided downstream of the extrusion die forcontrolling to some degree the manner in which the pressure applied tothe extrusion composition is reduced. The extruded and expanded polymerfoam material may be subjected to additional processing such ascalendaring, water immersion, cooling sprays, or other operations tocontrol the thickness and other properties of the resulting polymer foammaterial.

In some embodiments, the polymer foams of the present disclosure areextruded polymer beads made by a bead extrusion method. Bead extrusionis similar to the extrusion process previously described. However, inbead extrusion, the extrusion die contains a plurality of small holessuch that the extrusion composition is extruded as beads. These beadsare typically in the range of about 0.05 mm to about 2.0 mm in diameter.Furthermore, the extrusion composition is not allowed to foam once thebeads containing the extrusion composition exit the extrusion die.Instead, the beads containing the extrusion composition are dischargedinto a coolant chamber or coolant bath, and the beads are rapidly cooledto below the glass transition temperature (T_(g)) of the extrusioncomposition. This rapid cooling prevents the extrusion composition inthe beads from foaming.

In some embodiments of bead extrusion, the matrix polymer, blowing agentcomposition, and optional additives are introduced to the extruder asdescribed above to form an extrusion composition. In some embodiment ofbead extrusion, the matrix polymer and optional additives are introducedto the extruder as described above to form an extrusion composition, butthe blowing agent composition is added to the extruded beads via apressure vessel after the beads have been extruded and cooled.

In some embodiments, the polymer foams of the present disclosure areexpanded polymer foams made by an emulsion or suspension polymerizationmethod. In some embodiments of expanded polymer foams, the matrixpolymer is polymerized from monomer dispersed in a liquid phase within areaction vessel. In some embodiments, a blowing agent composition isadded to the polymer mixture by adding the blowing agents as diluentswithin the liquid phase within the reaction vessel during thepolymerization reaction. In some embodiments, a blowing agentcomposition is used as the liquid phase within the reaction vesselduring the polymerization reactions. In some embodiments, the blowingagent composition is added to the polymer mixture in a pressure vesselafter the polymerization reaction has been completed.

This extrusion composition is then forced through an extrusion die andexits the die into a region of reduced pressure (which may be belowatmospheric pressure), thereby allowing the blowing agent to expand andproduce a polymer foam layer or slab. The polymer foam may be subjectedto additional processing such as calendaring, water immersion, coolingsprays or other operations to control the thickness and other propertiesof the resulting polymer foam product.

Polymer Foam

The manufacturing process produces a polymer foam. In some exemplaryembodiments, the manufacturing process of the foamable polymer mixtureproduces rigid, substantially closed cell, polymer foam boards preparedby an extruding process. Extruded foams have a cellular structure withcells defined by cell membranes and struts. Struts are formed at theintersection of the cell membranes, with the cell membranes coveringinterconnecting cellular windows between the struts.

In some exemplary embodiments, the foams have an average density of lessthan 5 pounds per cubic foot (“pcf”), or less than 4 pcf, or less than 3pcf. In some exemplary embodiments, the polymer foam has a density fromabout 1 pcf to about 4.5 pcf, including from about 1.2 pcf to about 4pcf, including from about 1.3 pcf to about 3.5 pcf, including from about1.4 pcf to about 3 pcf, including from about 1.5 pcf to about 2.8 pcf,including from about 1.6 pcf to about 2.6 pcf, including from about 1.7pcf to about 2.5 pcf, including from about 1.8 pcf to about 2.4 pcf,including from about 1.9 pcf to about 2.3 pcf, including from about 2.0pcf to about 2.2 pcf. In some exemplary embodiments, the polymer foamhas a density of about 2.0 pcf, or lower than 2.0 pcf.

It is to be appreciated that the phrase “substantially closed cell” ismeant to indicate that the foam contains all closed cells or nearly allof the cells in the cellular structure are closed. In some embodiments,not more than 20% of the cells are open cells, and particularly, notmore than 10%, or more than 5% are open cells, or otherwise “non-closed”cells. In some embodiments, from about 0.5% to about 4.0% of the cellsare open cells, including from about 0.75% to about 3.5%, including fromabout 1.0% to about 3.2%, including from about 1.2% to about 3.0%,including from about 1.5% to about 2.8%, including from about 1.75% toabout 2.5%, and including from about 2.0% to about 2.25% of the cellsare open cells. The closed cell structure helps to increase the R-valueof a formed, foamed insulation product. It is to be appreciated,however, that it is within the purview of the present invention toproduce an open cell structure.

The average cell size of the matrix polymer cells in the inventive foamand foamed products may be from about 0.05 mm (50 μm) to about 0.4 mm(400 μm), including from about 0.1 mm (100 μm) to about 0.3 mm (300 μm),including from about 0.11 mm (110 μm) to about 0.25 mm (250 μm),including from about 0.12 mm (120 μm) to about 0.2 mm (200 μm),including from about 0.13 mm (130 μm) to about 0.18 mm (180 μm), andincluding from about 0.14 mm (140 μm) to about 0.16 mm (160 μm). Theinventive foam may be formed into an insulation product such as a rigidinsulation board, insulation foam, packaging product, and buildinginsulation or underground insulation (for example, highway, airportrunway, railway, and underground utility insulation).

The inventive foamable polymer mixture additionally may produce polymerfoams that have a high compressive strength, which defines the capacityof a foam material to withstand axially directed pushing forces. In someembodiments, the inventive foam compositions have a compressive strengthwithin the desired range for polymer foams, which is from about 6 psiand 120 psi. In some embodiments, the inventive foamable polymer mixtureproduces foam having a compressive strength from about 10 psi and about110 psi, including from about 20 psi to about 100 psi, including fromabout 25 psi to about 90 psi, including from about 30 psi to about 80psi, including from about 35 psi to about 70 psi, including from about40 psi to about 60 psi, including from about 45 psi to about 50 psi.

The inventive foamable polymer mixture additionally may produce polymerfoams that have a high level of dimensional stability. For example, thechange in dimension in any direction is 5% or less, such as 3% or less,2% or less, and 1.5% or less. As used herein, the average cell size isan average of the cell sizes as determined in the X, Y, and Zdirections. In particular, the “X” direction is the direction ofextrusion, the “Y” direction is the cross machine direction, and the “Z”direction is the thickness. In the present invention, the highest impactin cell enlargement is in the X and Y directions, which is desirablefrom an orientation and R-value perspective. In addition, furtherprocess modifications would permit increasing the Z-orientation toimprove mechanical properties while still achieving an acceptablethermal property. The inventive polymer foam can be used to makeinsulation products such as rigid insulation boards, insulation foam,and packaging products.

Additionally, the inventive foam composition produces polymer foams thathave insulation values (R-values) per inch of at least 4, or from about4 to about 7. R-value, or total thermal resistance, is the measure ofthe resistance of heat transfer. The method of determining R-value isdescribed as follows. Thermal conductivity, k, is defined as the theratio of the heat flow per unit cross-sectional to the temperature dropper unit thickness, with the US unit:

$k = \frac{{Btu} \cdot {in}}{{hr} \cdot {ft}^{2} \cdot {{\,^{{^\circ}}F}.}}$

and the metric unit:

$k = \frac{W}{m \cdot K}$

The heat transfer through an insulating material can occur through solidconductivity, gas conductivity, radiation, and convection. The totalthermal resistance (R-value), R is the measure of the resistance to heattransfer, and is determined as:

R=t/k

where t=thickness.

The thermal conductivity k, after the inventive foam has aged 7 days, isfrom about 0.16 to about 0.18 Btu·in/hr·ft²·° F., including from about0.162 to about 0.178, including from about 0.164 to about 0.176,including from about 0.166 to about 0.174, including from about 0.168 toabout 0.172, including about 0.170 Btu·in/hr·ft²·° F. The thermalconductivity k, after the inventive foam has aged 60 days, is from about0.17 to about 0.185 Btu·in/hr·ft²·° F., including from about 0.172 toabout 0.184, including from about 0.174 to about 0.182, including fromabout 0.175 to about 0.181, including from about 0.176 to about 0.180,including about 0.178 Btu·in/hr·ft²·° F.

EXAMPLES Example 1

A series of experiments were conducted to form 1.0 inch extrudedpolystyrene (XPS) foam samples using various hydrocarbons as co-blowingagents with HFO-1234ze. The hydrocarbon co-blowing agents testedincluded n-butane, isobutane, n-pentane, isopentane, and cyclopentane.For each foam sample, the formulation comprised 98.5 wt. % polystyrene,1 wt. % flame retardant, 0.5 wt. % infrared attenuation agent, and 7.8wt. % blowing agent composition. The amount of each blowing agentcomponent is given in wt. % of the total composition, and in number ofmoles per 100 g of matrix polymer. The blowing agent compositionformulations and physical properties of each test sample are given inTables 1-5 below.

TABLE 1 Foam formulations with n-butane and HFO-1234ze HFO- n- Total7-days HFO- 1234ze n- butane Total BA Foam k-factor Sample 1234ze(moles/ butane (moles/ BA (moles/ Density (Btu · in/ No. (%) 100 g) (%)100 g) (%) 100 g) (lb/ft³) h · ft² · ° F.) A-1 7.55 0.0662 0.25 0.00437.80 0.0705 2.31 0.1685 A-2 7.33 0.0640 0.50 0.0086 7.80 0.0726 2.310.1685 A-3 7.05 0.0618 0.75 0.0129 7.80 0.0747 2.31 0.1679 A-4 6.800.0596 1.00 0.0172 7.80 0.0811 2.32 0.1681 A-5 6.30 0.0553 1.50 0.02587.80 0.0853 2.24 0.1687 A-6 5.80 0.0509 2.00 0.0344 7.80 0.0853 2.190.1730

TABLE 2 Foam formulations with isobutane and HFO-1234ze HFO- Iso- Total7-days HFO- 1234ze Iso- butane Total BA Foam k-factor Sample 1234ze(moles/ butane (moles/ BA (moles/ Density (Btu · in/ No. (%) 100 g) (%)100 g) (%) 100 g) (lb/ft³) h · ft² · ° F.) B-1 7.55 0.0662 0.25 0.00437.80 0.0705 2.24 0.1709 B-2 7.33 0.0640 0.50 0.0086 7.80 0.0726 2.240.1698 B-3 7.05 0.0618 0.75 0.0129 7.80 0.0747 2.26 0.1696 B-4 6.800.0596 1.00 0.0172 7.80 0.0811 2.25 0.1689 B-5 6.30 0.0553 1.50 0.02587.80 0.0853 2.21 0.1694 B-6 5.80 0.0509 2.00 0.0344 7.80 0.0853 2.280.1712

TABLE 3 Foam formulations with n-pentane and HFO-1234ze HFO- n- Total7-days HFO- 1234ze n- pentane Total BA Foam k-factor Sample 1234ze(moles/ pentane (moles/ BA (moles/ Density (Btu · in/ No. (%) 100 g) (%)100 g) (%) 100 g) (lb/ft³) h · ft² · ° F.) C-1 7.55 0.0662 0.25 0.00357.80 0.0697 2.28 0.1656 C-2 7.33 0.0640 0.50 0.0069 7.80 0.0710 2.220.1670 C-3 7.05 0.0618 0.75 0.0104 7.80 0.0722 2.23 0.1672 C-4 6.800.0596 1.00 0.0139 7.80 0.0735 2.26 0.1667 C-5 6.30 0.0553 1.50 0.02087.80 0.0761 2.23 0.1679 C-6 5.80 0.0509 2.00 0.0277 7.80 0.0786 2.220.1685

TABLE 4 Foam formulations with isopentane and HFO-1234ze HFO- Iso- Total7-days HFO- 1234ze Iso- pentane Total BA Foam k-factor Sample 1234ze(moles/ pentane (moles/ BA (moles/ Density (Btu · in/ No. (%) 100 g) (%)100 g) (%) 100 g) (lb/ft³) h · ft² · ° F.) D-1 7.55 0.0662 0.25 0.00437.80 0.0705 2.33 0.1677 D-2 7.33 0.0640 0.50 0.0086 7.80 0.0726 2.250.1710 D-3 7.05 0.0618 0.75 0.0129 7.80 0.0747 2.25 0.1698 D-4 6.800.0596 1.00 0.0172 7.80 0.0811 2.26 0.1695 D-5 6.30 0.0553 1.50 0.02587.80 0.0853 2.21 0.1673 D-6 5.80 0.0509 2.00 0.0344 7.80 0.0853 2.210.1669

TABLE 5 Foam formulations with cyclopentane and HFO-1234ze HFO- Cyclo-Total 7-days HFO- 1234ze Cyclo- pentane Total BA Foam k-factor Sample1234ze (moles/ pentane (moles/ BA (moles/ Density (Btu · in/ No. (%) 100g) (%) 100 g) (%) 100 g) (lb/ft³) h · ft² · ° F.) E-1 7.55 0.0662 0.250.0036 7.80 0.0698 2.28 0.1669 E-2 7.33 0.0640 0.50 0.0071 7.80 0.07122.24 0.1670 E-3 7.05 0.0618 0.75 0.0107 7.80 0.0725 2.19 0.1674 E-4 6.800.0596 1.00 0.0143 7.80 0.0739 2.17 0.1673 E-5 6.30 0.0553 1.50 0.02147.80 0.0767 2.21 0.1665 E-6 5.80 0.0509 2.00 0.0285 7.80 0.0794 2.220.1665

A graph of the thermal insulation (7-days k-factor) for each foamformulation is shown in FIG. 1. For each formulation, the thermalinsulation properties remain relatively constant as the amount of HFO isvaried. There does not appear to be an immediate advantage to increasingthe weight percent of HFO blowing agent (an expensive ingredient)relative to the hydrocarbon co-blowing agent in freshly-manufacturedpolymer foams.

Example 2

The foam formulations of Example 1 were analyzed for thermal insulationproperties as the samples aged. The thermal aging curves for C1-C6 (thefoam formulations comprising n-pentane as the co-blowing agent) areshown in FIG. 2. Thermal aging curves for the other foam formulations ofExample 1 follow the same general trends as shown in FIG. 2.

As the HFO/n-pentane foams age, the foam sample with the highestconcentration of HFO (sample C-1) has slightly better thermal insulatingproperties than the foam samples with lower concentrations of HFO(samples C-2 to C-6). However, it should be noted that sample C-1 hasabout 30% more HFO than does sample C-6 (7.55 wt. % versus 5.80 wt. %),but the k-factor for C-1 at 60 days is only about 2% better than C-6(0.181 versus 0.185). There does not appear to be a large long-termadvantage as the polymer foam ages to increasing the weight percent ofHFO blowing agent (an expensive ingredient) relative to the hydrocarbonco-blowing agent.

Example 3

The foam formulations from Example 1 comprising 5.8 wt. % HFO and 2.0wt. % hydrocarbon (i.e., samples A-6, B-6, C-6, D-6, and E-6) werecompared for thermal insulating properties as they aged. As acomparative example, a similar foam comprising 5.80 wt. % HFO-1234ze and2.00 wt. % HFC-152 was also evaluated for its thermal insulatingproperties as it aged. The thermal aging curves for these samples areshown in FIG. 3.

The foam sample comprising HFO and isobutane (sample B-6) has the bestthermal insulating properties, with a k-factor of about 0.180Btu·in/h·ft²·° F. after 60 days. The foam sample comprising HFO andisopentane (sample D-6) has the next best thermal insulating properties,with a k-factor of about 0.183 Btu·in/h·ft²·° F. after 60 days. The foamsamples with n-butane, n-pentane, and cyclopentane (samples A-6, C-6,and E-6, respectively) have comparable thermal insulating properties,with k-factors of about 0.184-0.185 Btu·in/h·ft²·° F. after 60 days. Thecomparative sample (sample COMP), with HFO and HFC, has the poorestthermal insulating properties, with a k-factor of about 0.188Btu·in/h·ft²·° F. after 60 days. These results suggest that polymerfoams using blowing agents comprising HFO and a branched hydrocarbon,such as isobutane or isopentane, have superior thermal insulatingproperties over similar foams using blowing agents comprising HFO andlinear or cyclic hydrocarbons, such as n-butane, n-pentane, orcyclopentane. Additionally, polymer foams using blowing agentscomprising HFO and a branched hydrocarbon, such as isobutane orisopentane, also have superior thermal insulating properties oversimilar foams using blowing agents comprising HFO and HFC, and excludingbranched hydrocarbons.

Example 4

The data presented in FIG. 3 for Example 3 was normalized to compare thehydrocarbon co-blowing agents on a molar (2.88 moles/100 g matrixpolymer) rather than weight (2.0 wt. %) basis in each composition. Thenormalized thermal aging curves are shown in FIG. 4. When normalized inthis way, the foams with isopentane, isobutane, and n-butane (samplesD-6, B-6, and A-6, respectively) have superior thermal insulatingproperties compared to the foams with n-pentane and cyclopentane(samples C-6 and E-6, respectively). The comparative sample (sampleCOMP), still has the poorest thermal insulating properties.

Example 5

A series of experiments were conducted to form extruded polystyrene(XPS) foam samples at the lowest possible densities, using HFO-1234zeblowing agent at 3.00 wt. % and various hydrocarbon co-blowing agents at4.80 wt. %. The hydrocarbon co-blowing agents tested included n-butane,isobutane, n-pentane, isopentane, and cyclopentane. The thickness of thesamples was held constant at 1.00 inch. For a 1.0 inch board the R-valueis 5 or thermal conductivity is 0.20 Btu·in/ft²·h·° F. The R-value isthe inverse of the thermal conductivity. The lower the thermalconductivity the higher the R-value. As a comparative example, a similarfoam comprising 3.00 wt. % HFO-1234ze and 4.80 wt. % HFC-152a was alsoevaluated for its thermal insulating properties as it aged. For eachfoam sample, the formulation comprised 98.5 wt. % polystyrene, 1 wt. %flame retardant, 0.5 wt. % infrared attenuation agent, and 7.8 wt. %blowing agent composition. The blowing agent composition formulationsfor each series of test samples are given in Tables 6 below.

TABLE 6 Foam formulations with 3.00 wt. % HFO-1234ze and 4.80 wt. %co-blowing agent HFO- n- Iso- n- Iso- Cyclo- HFC- HFO- 1234ze n- butaneIso- butane n- pentane Iso- pentane Cyclo- pentane HFC- 152a Sample1234ze (moles/ butane (moles/ butane (moles/ pentane (moles/ pentane(moles/ pentane (moles/ 152a (moles/ No. (%) 100 g) (%) 100 g) (%) 100g) (%) 100 g) (%) 100 g) (%) 100 g) (%) 100 g) F-1 3.00 0.0263 4.800.0826 — — — — — — — — — — F-2 3.00 0.0263 — — 4.80 0.0826 — — — — — — —— F-3 3.00 0.0263 — — — — 4.80 0.0665 — — — — — — F-4 3.00 0.0263 — — —— — — 4.80 0.0665 — — — — F-5 3.00 0.0263 — — — — — — — — 4.80 0.0684 —— F-6 3.00 0.0263 — — — — — — — — — — 4.80 0.0727

FIG. 5 shows a graph of the thermal aging curves for foams at variousdensities using a blowing agent of 3.00 wt. % HFO and 4.80 wt. %isobutane. The foams each included less than 0.03 moles of HFO-1234ze.The foam sample with a density of 2.52 lb/ft³ has the highest thermalresistance, with a k-factor of about 0.179 Btu·in/h·ft²·° F. after 180days. However, the foams with lower densities also had acceptablethermal resistance values, with 180-day k-factors ranging from about0.180 to about 0.194 Btu·in/h·ft²·° F. for foams with densities from2.25 to 1.43 lb/ft³, respectively. As mentioned above, an R-value of 5for a 1.0 inch board has a thermal conductivity of 0.20 Btu·in/ft²·h·°F. Thus, each foam sample achieved an R-value of at least 5.

FIG. 6 shows a graph comparing foams containing the differenthydrocarbon co-blowing agents at various densities. For all foamdensities, Samples F-2 and F-4, which contain the co-blowing agentsisobutane and isopentane, respectively, have better thermal resistance(lower k-factors) after 7 days than do Samples F-1 and F-3, whichcontain n-butane and n-pentane, respectively. The dotted line at 1.75lb/ft³ density designates the target density for most commercial foams.FIG. 6 shows that foam products with densities substantially lower than1.75 lb/ft³ can have acceptable thermal resistance when isobutane orisopentane are used as co-blowing agents and an HFO as a blowing agent.

Example 6

A series of experiments were conducted to form extruded polystyrene(XPS) foam samples using various concentrations of HFO-1234ze,isobutane, and carbon dioxide. The target foam density was 2.25+/−0.05lb/ft³. The CO₂ was used to maintain the total blowing agent at 7.8 wt.% of the foamable material, while the concentrations of HFO-1234ze andisobutane was varied. The ratio between the HFO and isobutane was keptconstant at 1.6. For each foam sample, the formulation comprised 98.5wt. % polystyrene, 1 wt. % flame retardant, 0.5 wt. % infraredattenuation agent, and 7.8 wt. % blowing agent composition. The amountof each blowing agent component is given in wt. % of the totalcomposition, and in number of moles per 100 g of matrix polymer. Theblowing agent composition formulations, foam density, 7-day k-factor ofeach sample is provided below in Table 7.

TABLE 7 Foam formulations containing various concentrations ofHFO-1234ze, isobutane and carbon dioxide. 7-days HFO- HFO- k-factorSample 1234ze 1234ze isobutane isobutane CO₂ CO₂ Density (Btu · in/ No(%) (moles) (%) (moles) (%) (moles) (lb/ft³) h · ft² · ° F.) G-1 3.000.0263 4.80 0.0826 0.000 0.0000 2.25 0.1685 G-2 2.90 0.0254 4.65 0.08000.125 0.0028 2.25 0.1694 G-3 2.81 0.0246 4.49 0.0773 0.250 0.0057 2.250.1695 G-4 2.71 0.0238 4.34 0.0747 0.375 0.0085 2.31 0.1699 G-5 2.620.0230 4.18 0.0719 0.500 0.0114 2.30 0.1705 G-6 2.52 0.0221 4.03 0.06930.625 0.0142 2.26 0.1708 G-7 2.42 0.0212 3.88 0.0668 0.750 0.0170 2.240.1713 G-8 2.33 0.0204 3.72 0.0640 0.850 0.0193 2.26 0.1739 G-9 2.230.0196 3.57 0.0614 1.000 0.0227 2.30 0.1767 G-10 1.85 0.0162 2.95 0.05081.500 0.0341 2.30 0.1801

The foams thermal aging curves with various concentrations ofHFO-1234ze, isobutane and carbon dioxide are shown in FIG. 7. The curvesshow that the thermal conductivity of the foam increases as theconcentration of the HFO-1234ze and isobutane is decreased and replacedwith carbon dioxide.

Although the invention has been described in the context of particularpolystyrene foam materials, the inventive method is also applicable toother polymer compositions and various combinations of blending agentsto obtain a variety of polymer foam materials. Example embodiments ofthe invention have been disclosed herein and, although specific termsare employed, they are used and are to be interpreted in a generic anddescriptive sense only and not for purpose of limitation. Accordingly,it will be understood by those of ordinary skill in the art that variouschanges in form and details of the disclosed apparatus and methods maybe made without departing from the spirit and scope of the invention asset forth in the following claims.

What is claimed is:
 1. A foamable polymer composition comprising: amatrix polymer composition comprising polystyrene; and a blowing agentcomposition comprising: from 1 to 5 wt. % of a hydrofluoroolefin (HFO)blowing agent comprising HFO-1234ze; from 0.05 to 1 wt. % of a branchedhydrocarbon blowing agent; and from 0.05 to 5 wt. % of ahydrofluorocarbon (HFC) blowing agent, wherein the foamable polymercomposition contains essentially no water, and wherein each wt. % isbased upon the total weight of the foamable polymer composition.
 2. Thefoamable polymer composition of claim 1, wherein the blowing agentcomposition consists of the HFO blowing agent, the branched hydrocarbonblowing agent, and the HFC blowing agent.
 3. The foamable polymercomposition of claim 1, wherein the branched hydrocarbon blowing agentis selected from the group consisting of: isobutane; isopentane;neopentane; isohexane; 3-methylpentane; 2,3-dimethylbutane; neohexane;isoheptane; 3-methylhexane; 2,2-dimethylpentane; 2,3-dimethylpentane;2,4-dimethylpentane; 3,3-dimethylpentane; 3-ethylpentane;2,2,3-trimethylbutane; and combinations thereof.
 4. The foamable polymercomposition of claim 3, wherein the branched hydrocarbon blowing agentconsists of isobutane.
 5. The foamable polymer composition of claim 1,wherein: the HFO blowing agent consists of HFO-1234ze; the branchedhydrocarbon blowing agent consists of isobutane; and the HFC blowingagent consists of 1,1-difluoroethane.
 6. The foamable polymercomposition of claim 1, wherein the foamable composition comprises lessthan 0.03 moles HFO blowing agent per 100 grams of matrix polymer.
 7. Afoamable polymer composition comprising: a matrix polymer compositioncomprising polystyrene; and a blowing agent composition comprising: from1 to 5 wt. % of a hydrofluoroolefin (HFO) blowing agent comprisingHFO-1234ze; from 0.05 to 1 wt. % of a branched hydrocarbon blowingagent; and from 0.05 to 5 wt. % of a co-blowing agent comprising carbondioxide, wherein the foamable polymer composition contains essentiallyno water, and wherein each wt. % is based upon the total weight of thefoamable polymer composition.
 8. The foamable polymer composition ofclaim 7, wherein the blowing agent composition consists of the HFOblowing agent, the branched hydrocarbon blowing agent, and the carbondioxide.
 9. The foamable polymer composition of claim 7, wherein thebranched hydrocarbon blowing agent is selected from the group consistingof: isobutane; isopentane; neopentane; isohexane; 3-methylpentane;2,3-dimethylbutane; neohexane; isoheptane; 3-methylhexane;2,2-dimethylpentane; 2,3-dimethylpentane; 2,4-dimethylpentane;3,3-dimethylpentane; 3-ethylpentane; 2,2,3-trimethylbutane; andcombinations thereof.
 10. The foamable polymer composition of claim 9,wherein the branched hydrocarbon blowing agent consists of isobutane.11. The foamable polymer composition of claim 7, wherein: the HFOblowing agent consists of HFO-1234ze; the branched hydrocarbon blowingagent consists of isobutane; and the co-blowing agent consists of carbondioxide.
 12. The foamable polymer composition of claim 7, wherein thefoamable composition comprises less than 0.03 moles HFO blowing agentper 100 grams of matrix polymer.
 13. A method of manufacturing polymerfoam, comprising: a) providing a matrix polymer composition comprisingpolystyrene; b) melting the matrix polymer composition in an extruder;c) injecting a blowing agent composition comprising into the moltenmatrix polymer composition within the extruder to form a foamablepolymer composition, wherein the blowing agent composition comprises:from 1 to 5 wt. % of a hydrofluoroolefin (HFO) blowing agent comprisingHFO-1234ze; from 0.05 to 1 wt. % of a branched hydrocarbon blowingagent; and from 0.05 to 5 wt. % of a co-blowing agent comprising ahydrofluorocarbon (HFC), carbon dioxide, or combinations thereof,wherein each wt. % is based upon the total weight of the foamablepolymer composition, wherein the foamable polymer composition containsessentially no water or carbon dioxide; and d) extruding the foamablepolymer composition to form a polymer foam.
 14. The method of claim 13,wherein the polymer foam has an R value from 4 to 7.